The invention described and claimed in this application relates to a solid fuel fired gas turbine system for generating electric power which includes a generator, a turbine for operating the generator, a combustion chamber for burning solid fuel to form heated gas under pressure for operating the turbine, and a continuously regenerating granular filter for removing particulate matter from the pressurized, heated gas. The granular filter is operable at high temperature and pressure as is particularly well suited for continuously cleaning the pressurized, hot gas used to operate the gas turbine without significant loss of gas pressure or temperature. The particular granular filter used in the present gas turbine system invention is the subject matter of copending application Ser. No. 647,471, filed Jan. 8, 1976 by Lear et al. Both the present invention and the invention of the aforementioned application Ser. No. 647,471 were made in the course of or under a contract with the United States Environmental Protection Agency and are owned by the United States of America.
Different types of filters or separators have been tried, but many have significant drawbacks which prevent them from being used. For example, inertial separators such as cyclones have been found not to be effective in removing micron or sub-micron size particles and since cyclones operate at a relatively high velocity, e.g. 50-150 feet/second, if the particulate material has a tendency to stick to surfaces dense deposits in the cyclone result.
Bag houses, where the gas is channeled through a finely meshed material to filter out the particulate material, are limited to relatively low temperatures because of the material used to form the bag. In addition, bag houses are not effective at velocities greater than 15 feet/min., which would require an excessively large filter area at great cost.
Electrostatic precipitators have found not to be effective because of their relatively large size and complex construction. In addition, electrostatic precipitators consume relatively high amounts of power and are sensitive to electrical properties of the particulate material to be removed from the gas. Although electrostatic precipitators have a relatively high maximum collection efficiency, the overall collection efficiency is not as great because of uneven gas flow distribution and particulate re-entrainment when the plates are cleaned.
It has been found that filters using a granular material as a filter medium offer significant advantages for use in a high temperature and pressure environment where high efficiency cleaning is necessary. However, no granular filters were known which operated continuously and efficiently for long periods of time under such conditions of high pressure and temperature.